1. Field of the Invention
The present invention relates to a golf shaft and a golf club.
2. Description of the Related Art
Existing mainstream golf club shafts include a carbon shaft and a steel shaft, and the users make a choice depending on their own physical capacities or characteristics and performances of material.
In recent years, the users tend to attach importance to decorative properties in addition to performances or characteristics when choosing a golf club.
Heretofore, those shafts had plain color, that is, the carbon shaft was black which was a self-color of carbon fiber, and the steel shaft was silver (metallic) obtained by plating process. However, in recent years, golf shafts decorated with various colors or patterns on the surfaces thereof by paint application or by metal coating process are increasing.
However, in the case of decorations on the surfaces of shafts by paint application or by metal coating process described above, when they are scratched or peeled off, they are not functional any more from an decorative point of view, and designs are limited anyway because they are two-dimensional decorations.
For example, the amateur golfers tend to choose the steel shaft that is used by so called leading professional golf players.
However, since the steel shaft is heavy in comparison with the carbon shaft, and thus the amateur golfers cannot handle the steel shaft skillfully, in many cases they use a carbon shaft that looks like a steel shaft by being painted or by being metal coated. However, as described above, the base can be exposed due to scratches or peeling, and thus the decorative effect to make it look as a steel shaft may be lost.
Differences of the characteristics between carbon shafts and steel shafts include, for example, a difference of oscillation damping rate.
In general, since oscillation damping rate of carbon shafts is high, the impact exerted at the time of meeting the ball is suppressed by bending of the shaft. However, there is a case where the shaft which is bent during the downswing cannot be maintained in its bent state and is restored to the original state during the course of downswing before the impact, whereby the golfer cannot take advantage of the head speed.
In contrast to it, since the oscillation damping rate of the steel shaft is low, the impact exerted at the time of meeting the ball is significant, and thus it might put a heavier physical burden on the golfer. However, bending of the shaft during downswing can be maintained and thus the golfer can take sufficient advantage of the head speed at the impact.
In other words, the carbon shaft and the steel shaft have completely opposite advantages and disadvantages with respect to each other due to the difference of characteristics as described above. Professional golfers or skilled amateur golfers can make use of advantages or these two types of shafts and make full use of their performances, while general amateur golfers can hardly make use of their advantages, but are subject to the disadvantages in many cases.
Accordingly, it is a subject of the invention to show excellent decorative properties of golf shafts as well as to maintain the same for a long time, and thus an object of the invention is to provide a golf shaft and a golf club in which the aforementioned subject is solved.
In addition to the aforementioned subjects, it is another subject to improve its usability, and thus another object of the invention is to provide a golf shaft and a golf club in which another subject is solved.
In order to achieve the objects, the invention employs the following technical measures.
A technical measure of the invention is to provide a golf shaft comprising an upper ply being transparent or at least having translucency to the extent that the interior surface is visible and a lower ply provided underneath the upper ply so that the surface configuration can be seen through the upper ply. (claim 1)
Another technical measure of the invention is to provide a golf shaft comprising an upper ply being transparent or at least having translucency to the extent that the interior surface is visible and a lower ply having a surface pattern being different from that of the upper ply provided underneath the upper ply so that the surface pattern can be seen through the upper ply. (claim 2)
In order to achieve another object of the invention, the invention employs the following technical measure.
The technical measure is a golf shaft comprising an upper ply being transparent or at least having translucency to the extent that the interior surface is visible and a lower ply having a surface pattern being different from that of the upper ply provided underneath the upper ply so that the surface pattern can be seen through the upper ply, characterized in that the upper ply and the lower ply are formed of materials having the different vibration characteristics from each other. (claim 3)
The factors to determine the vibration characteristics of material include, for example, specific gravity, rigidity, hardness, and oscillation damping rate.
Material being transparent or at least having translucency to the extent that the interior surface is visible includes glass fiber pre-preg, epoxy resin, phenol resin, thermosetting resin such as unsaturated polyester.
The term xe2x80x9ctransparentxe2x80x9d used here means the extent that the internal surface can be clearly viewed including colorless transparent and colored transparent, and the term xe2x80x9ctranslucencyxe2x80x9d used here means colored state to the extent that at least the internal surface can be viewed mistily.
When employing colored transparency, preferably, glass fiber pre-preg resin or thermosetting resin is colored in advance so that the entire thickness of the upper ply is colored, thereby preventing the color of the upper ply from being diminished.
By providing the lower ply with a substantially solid configuration which is different from that of the upper ply the substantially solid configuration can be seen through the upper ply (claim 4 and claim 6), and decoration having depth and spatial effect appears on the golf shaft.
The substantially solid configurations includes, for example, a rough configuration, a stepped configuration, and a polygonal configuration. When employing such solid configurations, the member to be used for the lower ply is formed into the exemplified configurations, or a separate member is adhered on the surface of the member to form it into a solid configuration.
In the case of adhering a separate member, various patterns including characters, graphics, patterns, and so on can be employed, and thus freedom of decoration can be expanded very much.
Alternatively, two-dimensional decoration such as characters, graphics, or patterns can also be employed optionally on the surface of the lower ply having a substantially solid configuration. With such arrangement, decoration on the lower ply is protected by the upper ply, and thus decoration on the lower ply is prevented from being diminished.
The upper ply includes a colorless transparent ply or a colored transparent ply on the surface thereof (claim 7 and claim 9), and such transparent ply is preferably a thin coated ply of transparent coating material applied thereon or of thermosetting resin, which serves to protect the ply immediately underneath thereof.
Preferably, the transparent ply is colorless transparent for example when the ply immediately underneath thereof is colorless transparent, colored transparent, or translucent, and is colored transparent in the same color when the ply immediately underneath thereof is colored transparent.
In terms of material having different oscillation damping rate, when the upper ply is formed of glass fiber pre-preg, or of thermosetting resin, the lower ply may be of metal material or carbon fiber pre-preg.
When metal material is employed, the surface of the metal material is preferably protected from rust by rustproof plating, metal film coating, or painting, which prevents the formation of rust on the lower ply and separation between the upper ply and the lower ply or deterioration of decorative property due to rust.
In addition, the surface of the metal material is preferably processed to increase adhesiveness with respect to thermosetting resin (including glass fiber pre-preg resin) used in the upper ply, which may prevent separation between the upper ply and the lower ply.
This process includes, for example, surface roughening of the metal material and plating process or metal evaporation process by the use of a metal that increases adhesiveness.
In the case where glass fiber pre-preg is used for the upper ply, surface roughening is preferably made so that the direction of roughness of on the rough surface coincides with the direction of the fiber of glass fiber pre-preg.
Metal to be used for plating process exemplified here includes zinc, nickel, aluminum, iron-based or copper-based metal.
In the case where carbon fiber is used for the lower ply, metal evaporation process may be made on the surface thereof in order to make metal color decoration to make the shaft look like a steel shaft.
In the case where the upper ply is formed by winding multiple layers of ply of glass fiber pre-preg, preferably, fibers of the pre-preg are laid in the same direction in order to ensure see-through of the upper ply.
In this case, preferably, adhesive ply is interposed between the upper ply and the lower ply at the ends of the shaft on the head side and on the grip side, which are susceptible to separation of glass fiber pre-preg, within the ranges that do not impair decorations on the surface of shaft. This adhesive ply achieves enhancement of the separation preventing effect of rough surface, as well as prevention of separation that often happens when cutting the ends of the shaft during molding of the shaft.
The adhesive ply used here is preferably thermosetting resin or glass fiber pre-preg impregnated with the same resin, for example glass fiber pre-preg impregnated with borax-based modified epoxy resin (ex. xe2x80x9cKS1020/P-162xe2x80x9d manufactured by Toho Tenax Co.,Ltd.).
When employing this pre-preg for the adhesive ply, it is formed by laying glass fibers in the bias direction, polymerizing them in the cross-linked state, and winding around the lower ply.
When the upper ply and the lower ply are formed of materials having different oscillation damping rates, the following effects are expected.
Taking a shaft in which the lower ply is made of steel and the upper ply is made of glass fiber pre-preg as an example, since the lower ply formed of steel is low in oscillation damping rate and the upper ply of glass fiber pre-preg has an oscillation damping rate higher than the lower ply, this shaft has such characteristics that the lower ply serves to maintain bending of the shaft generated during the downswing to sufficiently take advantage of the head speed at the impact, and the upper ply serves to help the restoring action of the lower ply to accelerate the restoring speed for absorbing the impact at the time of meeting the ball, so that the physical burden to the golfer is alleviated.
Therefore, by employing a golf shaft described in claim 1 to claim 9 of the invention in a golf club (claim 10 to claim 18), a golf club which is quite favorable in appearance and in usability is obtained.